BackgroundDue to the climate change of the past few decades, some agricultural areas in the world are now experiencing new climatic extremes. For soybean, high temperatures and drought stress can potentially lead to the “green seed problem”, which is characterized by chlorophyll retention in mature seeds and is associated with lower oil and seed quality, thus negatively impacting the production of soybean seeds.ResultsHere we show that heat and drought stress result in a “mild” stay-green phenotype and impaired expression of the STAY-GREEN 1 and STAY-GREEN 2 (D1, D2), PHEOPHORBIDASE 2 (PPH2) and NON-YELLOW COLORING 1 (NYC1_1) genes in soybean seeds of a susceptible soybean cultivar. We suggest that the higher expression of these genes in fully mature seeds of a tolerant cultivar allows these seeds to cope with stressful conditions and complete chlorophyll degradation.ConclusionsThe gene expression results obtained in this study represent a significant advance in understanding chlorophyll retention in mature soybean seeds produced under stressful conditions. This will open new research possibilities towards finding molecular markers for breeding programs to produce cultivars which are less susceptible to chlorophyll retention under the hot and dry climate conditions which are increasingly common in the largest soybean production areas of the world.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0729-0) contains supplementary material, which is available to authorized users.

RESUMOO presente trabalho teve por objetivo avaliar a germinação e o vigor de sementes de crambe, sob condições de estresse hídrico induzidas por soluções de polietileno glicol. As sementes foram colocadas para germinar em substrato embebido com soluções de polietileno glicol, utilizando-se os potenciais osmóticos de 0 (controle), -0,2; -0,4; -0.6; -0.8; -1,0; -1,2 e -1,4MPa. Avaliou-se a germinação das sementes pela porcentagem de plântulas normais e porcentagem de emissão de raiz primária, e o vigor pelo tempo médio de germinação, índice de velocidade de germinação, freqüência relativa de germinação e índice de sincronização da germinação. Observou-se que potenciais osmóticos mais negativos promoveram redução significativa na germinação e no vigor das sementes de crambe, não havendo formação de plântulas normais em potenciais inferiores a -0,6 MPa. UNITERMOS:Polietileno glicol, potencial osmótico, água, biodiesel. TEIXEIRA, R.N.; TOLEDO, M.Z.; FERREIRA, G.; CAVARIANI, C; JASPER, S.P. CRAMBE SEEDS GERMINATION AND VIGOR UNDER WATER STRESS 2 ABSTRACTThis study aimed to evaluate crambe seeds germination and vigor under water stress conditions induced by polyethylene glycol solutions. The seeds were germinated on substrate moistened with polyethylene glycol solutions, using the osmotic potentials of 0 (control), -0.2, -0.4, -0.6, -0.8, -1.0, -1.2 and -1.4 MPa. The seeds germination was evaluated by normal seedlings and root emission percentages. Vigor was evaluated by germination average time, relative frequency, velocity and synchronization index. It was observed that more negative osmotic potential caused significant reduction in crambe seed germination and vigor, and no normal seedlings was observed at potentials below -0.6 MPa.

ABSTRACT. Crambe is a promising crop for biodiesel production, mainly due to the high oil content of its seeds. However, there have been no effective methodologies for evaluating the physiological quality of crambe seeds. Seed lots have not been compared, especially by vigor tests, such as the accelerated aging. The objective of this study was to evaluate the effects of high temperature and exposure periods on the physiological quality and enzymatic activity of crambe seeds during the accelerated aging test. Two lots of crambe seeds of the Brilhante cultivar were analyzed by tests of moisture content, weight of 1,000 seeds, germination, first count, electrical conductivity, enzymatic activity (peroxidase and superoxide dismutase) and seedling length. All tests were carried out before and after the accelerated aging, which evaluated different temperatures (38, 40 and 42ºC) and exposure periods (24, 48 and 72 hours). The experimental design was completely randomized with four replications. Variance analysis and mean comparison through the Tukey and Dunnet tests (p ≤ 0.05) were applied for statistical analysis and means were also submitted to the linear correlation test. It was concluded that the interaction between temperature and exposure period affects the physiological quality and enzymatic activity of crambe seeds. We also conclude that the best conditions of temperature and exposure period for evaluating the physiological quality of crambe seeds through the accelerated aging test depend on genotype.Keywords: Crambe abyssinica, germination, vigor, deterioration. RESUMO.Qualidade fisiológica e atividade enzimática de sementes de crambe, após o envelhecimento acelerado. O crambe é uma cultura promissora para produção de biodiesel, principalmente pelo alto conteúdo de óleo de suas sementes. No entanto, não há metodologias estabelecidas para avaliar a qualidade fisiológica das sementes desta espécie e lotes não podem ser comparados, especialmente por testes de vigor, como o de envelhecimento acelerado. O objetivo da presente pesquisa foi avaliar o efeito da alta temperatura e do período de exposição durante o teste de envelhecimento acelerado na qualidade fisiológica e atividade enzimática de sementes de crambe. Dois lotes de sementes de crambe, cultivar Brilhante, foram analisados por meio dos testes de teor de água, massa de 1.000 sementes, germinação, primeira contagem, condutividade elétrica, atividade enzimática (peroxidase e superóxido dismutase) e comprimento de plântulas. As avaliações foram conduzidas antes e após o envelhecimento acelerado, que foram testadas diferentes temperaturas (38, 40 e 42ºC) e períodos de exposição (24, 48 e 72h). O delineamento experimental foi o inteiramente casualizado com quatro repetições. Os dados foram submetidos à análise de variância e as médias foram comparadas pelo teste de Tukey (p ≤ 0.05). O teste de Dunnet (p ≤ 0.05) foi utilizado para comparar os valores da testemunha (antes do envelhecimento acelerado) com cada valor médio individualmente. O teste de correlação lin...

O objetivo deste estudo foi avaliar os possíveis efeitos alelopáticos da massa seca de plantas de capim-colchão (Digitaria horizontalis), incorporadas ao solo em diferentes densidades, sobre a germinação e o crescimento inicial de milho, girassol e triticale. O experimento foi realizado em casa de vegetação, e as parcelas foram constituídas de uma planta, conduzida em vasos com capacidade para 2,5 L, dispostos inteiramente ao acaso. Material seco de capim-colchão nas quantidades equivalentes a 0, 2,5, 5,0 e 10 t ha-1 foi incorporado à terra. A emergência foi avaliada diariamente até 10 dias após a semeadura, quando se calculou a porcentagem final de emergência e o índice de velocidade de emergência (IVE). A altura e a massa seca das plantas foram avaliadas 35 dias após a semeadura. A incorporação da palhada da planta daninha não interferiu na germinação e no IVE das espécies avaliadas. A massa seca e a altura de plantas de todas as espécies foram influenciadas pela palhada, decrescendo de acordo com o aumento da concentração da palhada incorporada ao solo, com exceção do triticale, que não teve alteração quanto à altura.

Millet is a species of the grass family used in cattle pastures, for hay, for silage, and in soil cover in no-tillage systems. However, studies on seed production and post-harvest techniques for this species have not been sufficiently developed, considering the demand for and potential of this crop. The objective of this study was to monitor the physiological quality of millet seeds stored in porous packaging. Millet seeds were stored under four ambient conditions (natural laboratory environment, dry chamber, refrigerator, and freezer). Physiological quality was evaluated by germination and vigor tests before and during storage each year, up to six years for the dry chamber and natural laboratory environment, and up to 12 years for the refrigerator and freezer. Analysis of variance was conducted on the data, which were in 4 × 6 and 2 × 12 (environment and storage period) factorial arrangements. The means of the environments were compared by the Tukey test (p ≤ 0.05) and the storage periods by regression analysis. The germination capacity of millet seeds is best conserved in a refrigerator and freezer, and they remain viable for up to twelve years of storage under these conditions.

Chlorophyll retention reduces the quality of soybean grain and seeds, but little is known about the relationship between this anomaly and the seed–seedling transition or classical genetic breeding. Taking this into account, we provide a new perspective about how greenish seeds are associated with genetic material. For that, we used seed–seedling transition measurements of nine commercial cultivars cultivated by different seed farmers. Our findings demonstrated that: (i) The anomaly of greening in soybean seeds seems to be more expressed as a function of thermal variation than rainfall; (ii) There are commercial cultivars with distinct sensitivity to the greening phenotype, indicating potential for classical breeding for the species; (iii) The seed–seedling transition is significantly modified by the presence of greenish seeds, and the diagnosis of their presence can be anticipated by the analysis of embryo protrusion.